1. Field of the Invention
The invention relates to a seal for use in a watertight connector and a molding method therefor.
2. Description of the Related Art
A watertight connector has a housing with a plurality of cavities. Terminal fittings and rubber plugs are secured to ends of wires and are accommodated in the respective cavities. Each rubber plug is dimensioned to seal the cavity when the terminal fitting is accommodated in the cavity formed in a housing. Some cavities may not require a terminal fitting. In these situations, dummy rubber plugs are prepared separately and are fit into the unused cavities. The outer circumferential surface of the typical dummy plug has three annular lips defining a wavy cross section in view an inserting force into the cavity, a holding force in the cavity and mold removal at the time of molding.
A sealed space between male and female connectors with dummy plugs may be compressed during connection the two connectors. Additionally, internal pressure may increase as air in the sealed space thermally expands during the use. Thus, there is a possibility that the dummy plugs will come out of the cavities against the holding forces. Accordingly, Japanese Patent Publication No. 3180026 discloses embedding auxiliary springs in the dummy plugs for assisting deformation of the dummy plugs to increase their diameters and to enhance the holding forces.
The biasing forces of the prior art auxiliary springs increase the diameters of the dummy plugs to enhance the holding forces. However, the projecting ends of the widened lips successively contact the opening edge at the entrance of the cavity while inserting the dummy plug into the cavity. This impedes a smooth insertion and can tear the lips. Therefore, there has been an earnest demand for further improvement.
Accordingly, an object of the invention is to provide an improved seal.